First trimester:
1. abdo trauma, no PV bleeding -- no anti-D required
2. pelvic trauma, or abdo trauma with PV bleeding -- give 250 IU anti-D

Do not need to Kleihauer-Betke test as the 250IU dose is a always sufficent dose as fetal circulating blood volume is so low in the 1st trimester.

After 13 weeks:
1. abdo or pelvic trauma -- give 625 IU anti-D and perform KB test in case further doses of Anti-D are needed.

C

First trimester

Rhesus D antigen is expressed on fetal RBC membrane from 30days gestation and therefore antiD should be given after any potential sensitising event in a Rh neg woman. There is little evidence on quantifying the risk in the first trimester and therefore different countries will have different policies. The UK guidelines advise not giving anti D for first trimester bleeding in an ongoing / viable pregnancy, whereas other countries will. The mini-dose (250iu) is sufficient in first trimester. Abdominal trauma is not considered a sensitising event in first trimester (uterus is in the pelvis).

After 13 weeks

After 13 weeks a larger dose (500iu or 625iu depending on which country you live) anti-D should be given after any sensitising event in a Rh neg woman regardless of whether there is bleeding and regardless of the Kleihauer. The Kleihauer will still need to be done after 13 weeks to quantify the feto-maternal haemorrhage if it is a large one and to help determine the amount of extra anti-D that is required. 250iu will suppress immune response to 5ml whole blood. However, the amount of blood required to sensitise is variable -- in prison studies on Rhneg men 0.1ml has been known to sensitise whereas in 20% of this population a whole unit 450ml of blood does not sensitise.

Other indications for Kleihauer for women regardless of Rhesus status is to:
1. quantify fetomaternal hemorrhage (FMH) in the presence of significant abdo trauma
2. assess the risk of fetal anaemia due to subclinical FMHs in a fetus with poor biophysical profile.